Don't Waste that Wastewater


Steve Fleischli
Water Program Director & Senior Attorney, Natural Resources Defense Council

 

The process of generating electricity uses a lot of water. In fact, thermoelectric power plants account for 41 percent of all freshwater withdrawals in the United States – more than any other source. This puts an enormous burden on local waterways and fisheries, and also makes power plants vulnerable to conditions such as drought and warmer surface water. But it doesn’t have to be this way – and wastewater utilities offer a solution.

Power plants use water to cool equipment and condense steam for turbines. Today, more than 500 U.S. power plants still rely on the most antiquated and destructive type of cooling system, known as “once-through” cooling, which draws water from a source waterbody to absorb heat and then discharges it at an elevated temperature. None of this type of cooling water is recycled.

Numerous reports document the vulnerability of once-through power plants to drought and high water temperatures. According to a recent U.S. Department of Energy report, climate change also means that thermoelectric power will require even more water for cooling to account for increasing temperature trends. Surface water temperatures will also be warmer, and drought will be more common in many regions of the country. All of that spells trouble for many power plants.

As I said above, the good news is that it doesn’t have to be this way. Most new power plants use closed-cycle cooling, which basically recycles cooling water with minimal water loss, or in the case of dry cooling, almost no water use at all. Another important technique that makes power plants more resilient to drought and high water temperatures is the use of reclaimed water (i.e., treated sewage) for cooling. That’s where the wastewater sector comes in.

The use of reclaimed water for power plant cooling dates back to the 1960s, and since 1975, California has encouraged the use of reclaimed wastewater for power plant cooling.

Today, 67 U.S. power plants use reclaimed wastewater for cooling purposes. The volume of treated wastewater used at these facilities ranges from 0.1 millions of gallons per day (MGD) to 55 MGD, with the average facility using between 0.5 MGD and 5 MGD. The largest current user of reclaimed water is the Palo Verde Nuclear Plant in Wintersburg, Ariz., which uses 55 MGD of reclaimed water for closed-cycle cooling makeup water. But a lot more can be done.

One important study found that nearly 50 percent of existing coal-fired power plants have sufficient reclaimed water available within a 10-mile radius, and 75 percent have sufficient reclaimed water available within a 25-mile radius. DOE also concludes that we can significantly reduce the water dependency of power plants by switching to dry and wet-dry hybrid cooling technologies and by using alternative water sources instead of freshwater. This is powerful evidence of the enormous potential for energy companies and water utilities to work together to reduce the environmental impacts from – and the water-related vulnerabilities to – power plants.

In short, it’s time to stop wasting our wastewater and instead use it to protect our nation’s energy supply.

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